US3812789A

US3812789A - Transportation system

Info

Publication number: US3812789A
Application number: US00298716A
Authority: US
Inventors: R Nelson
Original assignee: LTV Aerospace Corp
Current assignee: LTV Aerospace Corp
Priority date: 1972-10-13
Filing date: 1972-10-13
Publication date: 1974-05-28
Anticipated expiration: 1991-05-28

Abstract

A transportation system having a roadway and a plurality of vehicles movable over the roadway, the roadway having parallel guide rails between which the vehicles move, the vehicles having pairs of front and rear wheels which are turned as required by individual guide and steering means engageable with the guide rails for guiding movement of the vehicles along each section of the track and for selectively steering or switching the vehicles from one section of the roadway to another which extends angularly therefrom.

Description

United States Patent [191 Nelson May 28, 1974 1 1 TRANSPORTATION SYSTEM [75] Inventor: Roy A. Nelson, Grand Prairie, Tex.

[73] Assignee: LTV Aerospace Corporation, Dallas,

Tex.

[22] Filed: Oct. 13, 197.2

[21] Appl. No.: 298,716

[52] US. Cl 104/130, 105/215 R, 104/24 S [51] Int. Cl B611) 5/02 [58] Field of Search....... 104/130, 96, 105, 88, 242,

[56] References Cited UNlTED STATES PATENTS 3,119,349 1/1964 Hampton 104/130 3,643,601 2/1972 Taylor 104/88 3,650,216 3/1972 Broome 104/130 X Primary ExaminerM. Henson Wood, Jr.

Assistant Examiner-D. W. Keen Attorney, Agent, or FirmWalter J. Jagmin; H. C. Goldwire; James M. Cate [5 7] ABSTRACT 13 Claims, 6 Drawing Figures iATENTEDm 28 I974 SHEET 1 OF 4 mmm 1 TRANSPORTATION SYSTEM This invention relates to transportation systems and more particularly to transportation systems having vehicles movable over a roadway of the system and to vehicles having guide and steering means for guiding and steering the vehicles during their movement over the roadway.

An object of this invention is to provide a new and improved transportation system having a roadway and vehicles movable thereover.

Another object is to provide a transportation system, of the type described wherein the roadway has a main section and at least one shunt section extending angularly from the main section, the sections of the roadway having parallel side guide rails and the vehicles having guide and steering wheels selectively engageable with the guide rails of the roadway sections for guiding the movement of the vehicles over each section and steering it from one section onto another as desired.

Still another object is to provide a transportation system, of the type described, which has switch means located along the roadway for selectively operating the steering wheels of the vehicles to cause them to move along desired sections of the roadway.

An important object of the invention is to provide a new and improved vehicle which has pairs of front and rear wheels and individual guide and steering means operatively associated with each pair of wheels cooperable with the guide rails of the system for guiding and steering the vehicle as it moves over the roadway of a transportation system.

Other objects and advantages will be apparent from the specification and claims and from the accompanying drawing illustrative of the invention.

In the drawing:

FIG. 1 is a top view of the chassis of a vehicle of the transportation system embodying the invention on the roadway thereof;

FIG. 2 is a front view of the system illustrated in FIG.

FIG. 3 is a side view, with some parts shown in section and some broken away, of the system illustrated in FIG. 1;

FIG. 4 is an enlarged sectional view taken on line 4-4 of H6. 1;

FIG. 5 is an enlarged sectional view taken on line 5-5 of FIG. 1; and,

FIG. 6 is a schematic top view of a portion of the transportation system embodying the invention.

Referring now to the drawings, the transportation system T embodying the invention includes a roadway R along whose top planar surface travel vehicles V of the system. The road may have several sections such as S1 and S2 and includes side tracks or guide rails such as 12 and 13b which define the main section S1 of the roadway and guiderails l4 and 15 which define a shunt section S2 of the roadway which curves away from the main section intermediate ends thereof. The guide rail 15 is connected to the guide rail 13a -by a curved guide rail 16 and the guide rail 14 is connected to the guide rail 13b by a curved guide rail 16. Switch ramp assemblies l8 and 19 whose function will be explained below are provided upstream of the intersection of the two sections.

Each of the vehicles V has a chassis 20 which includes a pair of longitudinally extending frame mem- 2

bers

21 and 22 connected at their front and rear ends by a pair of

transverse members

23 and 24 and by intermediate

transverse members

24a and 24b. The chassis at its right rear corner has a kingpin housing 25 whose bracket 26 is connected by means of bolts 27 to the bracket 28 on the outer end of the horizontal arm 29 of the vertical comer post 30 of the chassis.

The right rear comer of the chassis is supported by a wheel 32 mounted for rotation on the horizontal axle 33 rigid with and extending horizontally from the vertical kingpin 34. The kingpin extends rotatably and vertically slidably through the housing 25 and the top and

bottom bearings

36 and 37 mounted in the housing. Downward movement of the housing, and therefore of the right rear chassis corner, relative to the kingpin is yieldably resisted by a spring 38 whose upper end bears against the top bearing and whose bottom end bears against the upwardly facing shoulder 39 of an external annular flange 40 of the kingpin.

The other corners of the chassis are supported by

wheels

32a, 32b and 32c which are connected to the left rear, left front, and right front chassis corners in the same manner as the wheel 32 is connected to the chassis right rear corner, and, accordingly, the elements of the means by which the

wheels

32a, 32b, and 32c are connected to the chassis have been provided with the same reference characters, to which the subscripts a, b and. c, respectively, have been added, as the corresponding elements of the means by which the wheel 32 is connected to the chassis right rear corner.

The kingpins 34 and 34a of the rear pair of wheels are connected by the usual tie rod linkage 44 which includes a transverse rod 45 whose opposite ends are pivotally connected, as at 46 and 46a, to the inner ends of the

arms

47 and 47a of the kingpins 34 and 34a, respectively. The kingpin arms extend horizontally forward, then upwardly and forwardly and then transversely inwardly to clear the

wheels

32 and 32a and the chassis 20.

The

front wheels

32b and 32c are similarly connected by a tie rod linkage 50 which includes a transverse rod 51 pivotally connected, as at 52 and 53, to the arms 47b and 470 of the

kingpins

34b and 34c.

It will be apparent, therefore, that the wheels of each pair of front and rear wheels will turn simultaneously and to a corresponding degree about the vertical axes of their respective kingpins.

The rear pair of wheels are steered by a guide and steering assembly 60 connected to the bottom ends of the kingpins 34 and 34a. The assembly 60 includes a bracket 62 having a vertical bore 63 in which is telescoped and rigidly secured, as by welding, the bottom end portion of the kingpin 34 below the axle 33.

A wheel mount assembly 65 is supported by the bracket 62 and has a mount bracket 66 comprising rear and

front plates

67 and 68 between and to which are rigidly secured shaft blocks 69 and 70 in any suitable manner, as by welding. The wheel mount assembly 65 is vertically movably secured to the kingpin bracket 62 by a pair of parallelogram arms or

links

71 and 72 pivotally connected to the bracket 62 by bolts 73 which extend through aligned apertures in the rear ends of the links and the

vertical flanges

74 and 75 of the bracket 62. The front ends of the links are similarly pivotally secured to the mount assembly plate 67 by bolts 76 which extend through aligned apertures in the top and 3 bottom pairs of lugs 77 extending rearwardly from the plate 67.

The mount assembly is yieldably supported by a leaf spring 80 whose rear end extends between the pair of lugs 81 of the brackets 62, and may be secured I axle or shaft 84 secured to the shaft block 70 and is adapted to engage the web of the

guide tracks

13b, 17 and 14. An outer steering wheel 85 is rotatably mounted on a shaft 86 which is vertically slidable in the bearing block 69 and which has lower and

top stops

87 and 88 engageable with the bearing block to limit vertical movement of the shaft and wheel 85 relative to the

plates

67 and 68.

The lower stop 87 extends rearwardly of the rear plate and has secured thereto a rod 89 whose upper end telescopes slidably into a sleeve 90 rigidly secured to the rear plate 67 in any suitable manner, as by welding. One end of a cable 91 is secured to the top end of the rod 89 and extends slidably through a flexible sheath 92 which is secured to the top end of the sleeve 90.

The guide and steering assembly 60 also includes a wheel mount assembly 65a which is connected to the kingpin 34a in the same manner as the wheel mount 65 and, accordingly, elements of the wheel mount.assembly 65a have been provided with the same reference numerals to which the subscript a has been added, as the elements of the wheel mount assembly 65.

The other end of the cable 91 is secured to a rod 89a mounted on the stop 87a which is telescoped in a sleeve 90a and the other end of the sheath 92 is secured to the sleeve90a of the wheel mount assembly 6511. Due to the provision of the cable or wire 91 whose movement is restrained by the sheath 92, when one of the steering wheels, for example, the steering wheel 85, is moved upwardly, the other steering wheel 85a will be moved downwardly and vice versa for a purpose to be described below.

The

front wheels

32b and 32c are similarly guided and steered by a guide and steering assembly which is identical to the guide and steering assembly 60 of the rear wheels and, accordingly, its elements have been provided with the same reference numerals, to which the prefix 1 has been added, as the corresponding elementsof the guide and steering assembly 60.

The guide wheels 83 and 183 of the

wheels

32 and 32c are engageable with the vertical web of the l-

beam guide rails

13b, 17 and 14, or 13b and 13a, between their

inner flanges

201 and 202, and, similarly the inner guide wheels83a and 1830 of the

left wheels

32a and 32b are engageable with the vertical web of the guide track 12 between its

inner flanges

203 and 204.

Upstream of any shunt section of the roadway, such as the shunt section S2, portions of the top

external flanges

205 and 206 of the guide rails 12 and 13b are ,removed at the locations of

switching assemblies

18 and 19, respectively, in order to permit vertical displacement of the steering wheels by the

switch assemblies

18 and 19.

The switch assembly 18 includes a ramp member 210 which is pivotally secured, as at 211, to a housing 212 embedded alongside the roadway. The ramp 210 is pivotable between the full line position and the broken line position, illustrated in F l6. 3, by an electric motor 214 suitably mounted in the housing 212 whose drive shaft 215 has eccentrically mounted thereon a circular cam 216. A drive rod 218 has its forward end pivotably connected, as at 219, to the dependent arm 220 of the ramp 210 and its other end is secured to a cam follower 221 whose hub 222 is telescoped on the cam 216..

It will be apparent that when the drive shaft 215 is rotated degrees from the position illustrated in FIG. 3, the switch ramp 210 is pivoted from the full line position to the broken line position in a counterclockwise manner about the axis of its pivotal connection 211 to the housing and when it is rotated through an additional 180, the ramp is rotated back to the full line position illustrated in FIG. 3. The ramp 210 when it is moved to its raised shunting or switching position, inclines upwardly and forwardly to engage the steering wheels 185 and then 85 as the vehicle moves forwardly and moves first the front steering wheel 185 and then the rear steering wheel 85 upwardly at the locations of the gaps in the outer flanges of the guide rail 13b. Simultaneously with such upward movement of the

steering wheels

185 and 85, the

left steering wheels

185a and 85a are moved downwardly to positions wherein they will engage the outer surface of the web of the guide rail 12. The drive shaft 214 of the motor shaft 214 extends through a suitable transverse passage 230 below the roadway and is journaled at its end remote from the motor 214 in a suitable pillow block 233.

The switching assembly 19 includes a switching ramp 2100 which is driven by a cam 216a in the same manner as the switch ramp 210 and, accordingly, the elements of the switching assembly 19 have been provided with the same reference numerals, to which the subscript a has been added, as the corresponding eiements of the switch assembly 18. The cam 2160 is displaced 180 from the orientation of the cam 216 so that the switch ramp 210a is in its raised operative position when the switch ramp 210 is in its lower operative position and vice versa.

The chassis has a carriage C connected thereto by

suitable linkages

241, 242, and 243 which provide for vertical adjustment of a secondary 244 of a linear induction motor whose primaries P are embedded in the roadway and by

pins

245 and 246 of the carriage which extend vertically upwardly and slidably into chassis brackets 247 and 248, respectively. Since the mounting means of the secondary 244 and details of the structure of the carriage C are not claimed in this application, they will not be described in greater detail herein but are fully described in the application of Roy A. Nelson being filed concurrently with the tiling of this application and assigned to the same assignee.

Assuming now that the vehicle V1 is moving in the direction indicated by the arrow in FIG. 6 along the main section S1 of the roadway, and approaches the location of the

switch assemblies

18 and 19, if the vehicle is to be switched or shunted off to the shunt section S2 of the roadway, the motor 214 is energized by a suitable control means, now shown, so as to move the ramp 210a to its upper position illustrated in H6. 2 and the ramp 210 will be moved to its lower position illustrated in FIG. 3. As the vehicle moves forwardly, the front left steering wheel 185a will be engaged by the ramp 210a and will be moved upwardly above the outer flange 204 of the guide rail 12. Such upward motion of the steering wheel 185a will cause downward movement of the steering wheel 185 and, the

front wheels

32b and 32c will be turned in clockwise directions about the axes of their kingpins 34b and 340 as the steering wheel 185 engages first the web of the guide rail 13b, then the web of the guide rail 17 and finally the web of the guide rail 14 as the vehicle moves forwardly. Similarly as the steering wheel 85a moves past the switch ramp 210a, it will be raised above the guide rail 12 while the right rear steering wheel 85 is lowered to position to engage the webs of rhe

guide rails

13b, 17 and 14 as the vehicle moves forwardly.

Once the right steering wheels move past the switch assembly 18, they move below the top external flange of the

guide rails

13b, 17 and 14 which then prevents accidental upwardly displacement of the right steering wheels.

If it has been desired to cause the vehicle Vl to continue to move forwardly in a straight line along the main section S1 past the shunt section S2, the ramp 210 would have been raised while the ramp 210a would have been lowered so that the engagement of the right steering wheels 185 and then 85 therewith would have caused the right steering wheels to be raised to inoperative position above the guide rail 13b and the left steering wheels 185 and then 85a to be lowered to their operative positions below the external top flange of the guide rail 12. As a result the vehicle would then move forwardly from between the

rails

12 and 13 to between the guide rails 12 and 13a and will not turn into the shunt section S2.

The operation of the motor 214 may of course be controlled by any suitable controls located either remote from the roadway or on the vehicle itself or alternatively a suitable mechanical means could be employed on the vehicle to move the steering wheels vertically as desired to cause proper switching of the vehicles to a shunt track or to permit them to move forwardly along the main section S1 instead of shunting over to the section S2. Such controls may also include limit switches such as the switch 250, FIG. 3, engageable by the switch ramp to deenergize the motor 214 whenever the ramps are moved to either of their two extreme positions.

It will be apparent that the vehicles are propelled along the roadway by a linear induction motor which includes the primaries P embedded, in the roadway, whose windings are energized by three phase alternating current, and the secondary 244 mounted on the carriage C of the vehicle. Other drive or propelling means could, of course, be used to drive the vehicles over the roadway such as that disclosed in the pending application of Roy A. Nelson, Ser. No. 258,701 filed June 1, 1972 for Transportation System.

It will also be apparent that the inner guide wheels, such as the guide wheels 83 and 83a of the rear wheels and 183 and 183a of the front wheels, guide movement of the vehicles along portions of the roadway between locations of intersections of two sections thereof, such as sections S1 and S2.

Due to the mounting of the

wheel mount assemblies

65, 65a, 165 and 165a to the kingpins of the wheels 32,

'32a, 32c and 32b, respectively, by the parallelogram links, the wheel mount assemblies may move vertically without causing any tilting of the axes of rotation of the guide and steering wheels. The yieldable support of these wheel mount assemblies by the leaf springs permits them to move vertically if the guide rails are displaced vertically from the surface of the roadway as at locations where the roadway intersects other roads along which automobiles or the like travel. At such 10- cations the guide rails may be lowered below the top surface of the roadway R and the guide and steering wheels would then be pushed downwardly as they engaged the top flanges of the guide rails as they moved into the downwardly curved portions, as at 230, FIG. 3, of the guide rails against the resistance of the leaf springs 80.

It will now be seen that a new and improved transportation system has been illustrated which includes a roadway having one or more sections which extend angularly from one another at intersections thereof and with each section having vertical parallel side guide rails and the vehicle having individual guide and steering means for its rear and its front wheels cooperable with the guide rails for turning the pairs of wheels as required to cause it to travel in a desired course over the roadway.

It will also be seen that the roadway may have associated therewith switch means for selectively operating the guide and steering means of the pairs of wheels of the vehicle to cause the vehicle to turn from one section of the roadway to another section.

It will further be seen that a newand improved vehicle has been illustrated and described which has guide and steering means cooperable with parallel vertical side guide rails of a roadway'for controlling the direction of movement of the vehicle over the roadway.

It will further be seen that the

wheel mount assemblies

65, 65a, and 165a are positioned forwardly of the wheels which they guide and steer so that the wheels are caused to start turning as they approach a shunt section to move properly thereonto.

While only one embodiment of the invention, together with modificationsthereof, has been described in detail herein and shown in the accompanying drawing, it will be evident that various further modifications are possible in the arrangement and construction of its components without departing from the scope of the invention.

What is claimed is:

l. A vehicle for travel over a roadway of a transportation system, the roadway having a main section and at least one shunt section extending angularlyfrom the main section, each section having parallel guide rails at the sides thereof extending upwardly therefrom, at least one rail of the shunt section connecting to one rail of the main section at the location of connection of the two sections, said vehicle including:

a chassis;

a pair of rear wheels supporting the rear end of the chassis and a pair of front wheels supporting the front end of the chassis, said wheels being rotatable about horizontal axes and turnable about vertical axes;

separate tiemeans connecting the wheels of each pair of front and rear wheels for causing the wheels of each pair of wheels to turn simultaneously; and

separate guide and steering means connected to each pair of wheels and operatively associated with the guide rails for guiding said wheels along each section of the roadway and for steering the wheels for switching movement of the vehicle from one section of the roadway to another, each of said wheels being mounted on a kingpin turnable about a vertical axis and each guide and steering means including;

separate wheel mount assembly connected to the kingpin of each wheel of a pair of the vehicle wheels, each wheel mount including a bracket, a guide wheel mounted on the bracket for rotation about a vertical axis and engageable with inner vertical surfaces of an adjacent guide rail and a steering wheel mounted on said bracket for limited vertical movement between a lower operative position wherein it is engageable with the outer vertical surface of the adjacent guide rail and an upper inoperative position wherein it is above the guide rail, said steering wheel being rotatable about a vertical axis; and

separate means interconnecting the steering wheels of each pair of steering wheels for causing one steering wheel of the pair to move to its lower operative position when the other steering wheel of the pair is moved to its upper inoperative position.

2. The vehicle of claim 1, wherein said bracket of each wheel mount assembly is spaced forwardly and connected to its associated kingpin by linkage means providing for vertical movement of said brackets relative to said kingpin.

3. The vehicle of claim 2, wherein said bracket of each wheel mount assembly is yieldably held against downward movement.

4. The vehicle of claim 3, wherein said means interconnecting said steering wheels includes a flexible member extending between said wheels and a sheath confining said flexible member, opposite ends of said flexible member being connected to the wheels for vertical movement therewith.

5. The vehicle of claim 1, wherein said means interconnecting said steering wheels includes a flexible member extending between said wheels and a sheath confining said flexible member, opposite ends of said flexible member being connected to the wheels for vertical movement therewith.

6. A transportation system including:

a roadway providing a substantially horizontal support surface, said roadway comprising a main section and at least one shunt section connected to and extending angularly from the main section;

parallel guide rails at the sides of each section of the roadway and a curved guide rail connecting adjacent ends of the guide rails of the main and shunt section at the location of connection of the shunt section to the main section at the side of the main section from which said shunt section extends angularly outwardly;

said guide rails having top inner and outer horizontal flanges, said outer flanges of the main section having slots therein at locations spaced from the location of connection of the shunt section to the main section; and a vehicle including:

a chassis;

a pair of rear wheels supporting the rear end of the chassis and a pair of front wheels supporting the front end of the chassis, said wheels being rotatable about horizontal axes and turnable about vertical axes; separate tie means connecting the wheels of each pair of front and rear wheels for causing the wheels of each pair of wheels to turn simultaneously; separate guide and steering means connected to each pair of wheels and operatively associated with the guide rails for guiding said wheels along each section of the roadway and for steering the wheels for switching movement of the vehicle from one section of the roadway to another, each wheel being mounted on a kingpin turnable about a vertical axis and each guide and steering means including: separate wheel mount assembly connected to the kingpin of each wheel of a pair of the vehicle wheels, each wheel mount including a bracket, a guide wheel mounted on the bracket for rotation about a vertical axis and engageable with inner vertical surfaces of an adjacent guide rail and a steering wheel mounted on said bracket for limited vertical movement between a lower operative position wherein it is engageable with the outer vertical surface of the adjacent guide rail and an upper inoperative position wherein it is above the guide rail, said steering wheel being rotatable about a vertical axis; and

separate means interconnecting the steering wheels of each pair of steering wheels for causing one steering wheel of the pair to move to its lower operative position-when the other steering wheel of the pair is moved to its upper inoperative position.

7. The transportation system of claim 6, wherein said bracket of each wheel mount assembly is spaced forwardly and connected to its associated kingpin by linkage means providing for vertical movement of said brackets relative to said kingpin.

8. The transportation system of claim 7, wherein said bracket of each wheel mount assembly is yieldably held against downward movement.

9. The transportation system of claim 8, wherein said means interconnecting said steering wheels includes a flexible member extending between said wheels and a sheath confining said flexible member, opposite ends of said flexible member being connected to the wheels for vertical movement therewith.

10. The transportation system of claim '9, and switch means for moving one steering wheel of a pair of steering wheels upwardly and the other downwardly at the locations of slots in the outer top flanges.

11. The transportation system of claim 10, wherein said switch means comprise switch ramp pivotally mounted below said slots and movable simultaneously between operative and inoperative positions wherein one ramp is in its operative position extending upwardly and forwardly in the direction of movement of the vehicle and in position to engage a steering wheel of a vehicle and move it upwardly of the adjacent outer flange and the other switch ramp is in a lower inoperative position.

12. The transportation system of claim 6, wherein said means interconnecting said steering wheels includes a flexible member extending between said wheels and a sheath confining said flexible member, opposite ends of said flexible member being connected to the wheels for vertical movement therewith.

13. The transportation of claim 12, and switch means for moving one steering wheel of a pair of steering wheels upwardly and the other downwardly at the locations of slots in the other top flanges.

Claims

1. A vehicle for travel over a roadway of a transportation system, the roadway having a main section and at least one shunt section extending angularly from the main section, each section having parallel guide rails at the sides thereof extending upwardly therefrom, at least one rail of the shunt section connecting to one rail of the main section at the location of connection of the two sections, said vehicle including: a chassis; a pair of rear wheels supporting the rear end of the chassis and a pair of front wheels supporting the front end of the chassis, said wheels being rotatable about horizontal axes and turnable about vertical axes; separate tie means connecting the wheels of each pair of front and rear wheels for causing the wheels of each pair of wheels to turn simultaneously; and separate guide and steering means connected to each pair of wheels and operatively associated with the guide rails for guiding said wheels along each section of the roadway and for steering the wheels for switching movement of the vehicle from one section of the roadway to another, each of said wheels being mounted on a kingpin turnable about a vertical axis and each guide and steering means including; a separate wheel mount assembly connected to the kingpin of each wheel of a pair of the vehicle wheels, each wheel mount including a bracket, a guide wheel mounted on the bracket for rotation about a vertical axis and engageable with inner vertical surfaces of an adjacent guide rail and a steering wheel mounted on said bracket for limited vertical movement between a lower operative position wherein it is engageable with the outer vertical surface of the adjacent guide rail and an upper inoperative position wherein it is above the guide rail, said steering wheel being rotatable about a vertical axis; and separate means interconnecting the steering wheels of each pair of steering wheels for causing one steering wheel of the pair to move to its lower operative position when the other steering wheel of the pair is moved to its upper inoperative position.

6. A transportation system including: a roadway providing a substantially horizontal support surface, said roadway comprising a main section and at least one shunt section connected to and extending angularly from the main seCtion; parallel guide rails at the sides of each section of the roadway and a curved guide rail connecting adjacent ends of the guide rails of the main and shunt section at the location of connection of the shunt section to the main section at the side of the main section from which said shunt section extends angularly outwardly; said guide rails having top inner and outer horizontal flanges, said outer flanges of the main section having slots therein at locations spaced from the location of connection of the shunt section to the main section; and a vehicle including: a chassis; a pair of rear wheels supporting the rear end of the chassis and a pair of front wheels supporting the front end of the chassis, said wheels being rotatable about horizontal axes and turnable about vertical axes; separate tie means connecting the wheels of each pair of front and rear wheels for causing the wheels of each pair of wheels to turn simultaneously; separate guide and steering means connected to each pair of wheels and operatively associated with the guide rails for guiding said wheels along each section of the roadway and for steering the wheels for switching movement of the vehicle from one section of the roadway to another, each wheel being mounted on a kingpin turnable about a vertical axis and each guide and steering means including: a separate wheel mount assembly connected to the kingpin of each wheel of a pair of the vehicle wheels, each wheel mount including a bracket, a guide wheel mounted on the bracket for rotation about a vertical axis and engageable with inner vertical surfaces of an adjacent guide rail and a steering wheel mounted on said bracket for limited vertical movement between a lower operative position wherein it is engageable with the outer vertical surface of the adjacent guide rail and an upper inoperative position wherein it is above the guide rail, said steering wheel being rotatable about a vertical axis; and separate means interconnecting the steering wheels of each pair of steering wheels for causing one steering wheel of the pair to move to its lower operative position when the other steering wheel of the pair is moved to its upper inoperative position.

10. The transportation system of claim 9, and switch means for moving one steering wheel of a pair of steering wheels upwardly and the other downwardly at the locations of slots in the outer top flanges.